The present invention relates generally to the design and construction of a centrifugal separation apparatus for separating a composition into a substantially solid portion and a substantially fluid portion. More particularly, the present invention has one form wherein a high speed centrifugal separator utilizes a centrifugal clutch to couple a plow blade assembly to a bowl containing a contaminated fluid for centrifugal separation into solids and liquids. Thereafter, the centrifugal clutch is disengaged and the plow blade assembly is driven relative to the bowl to dislodge the solids adhered to the bowl.
It is well known that in a centrifugal separator the separation of the solids and liquids in a contaminated fluid is accomplished by pumping the contaminated fluid into a high speed rotating bowl. The high speed rotation of the bowl creates centrifugal gravitational forces that cause the contaminated fluid to be displaced radially outward against the bowl wall. Since the bowl is rotating at a high rotational speed the solids tend to adhere to the bowl wall, while the substantially purified liquid exits through a discharge opening.
The centrifugal separator bowl must be periodically cleansed to remove the solids adhered to the bowl during the separation process. Failure to maintain the bowl in a dynamically balanced state and/or not overloaded with solid deposits can result in problems, such as: premature wear and failure of bearings, bushings, and seals; inefficient solid and liquid separation; overloading of the bowl drive motor; and overloading of the plow blade assembly drive motor. Prior designers of centrifugal separators have generally incorporated a mechanical plow blade within the bowl to remove accumulated deposits in an attempt to minimize problems associated with an overloaded and/or unbalanced bowl.
In many prior centrifugal separators the mechanical plow blade assembly is actuated at predetermined time intervals. A litany of disadvantages stem directly from having the cleaning of the centrifugal separator bowl occurring only at predetermined time intervals. More specifically, one disadvantage is associated with the inevitable variations in solid content within the contaminated fluid than can lead to mistiming of when the bowl cleaning is needed. Results of the mistiming include the overloading of the bowl with solids because too must processing time has elapsed since the last actuation of the cleaning cycle, or the inefficient processing of the contaminated fluid because the apparatus is cleansed when small amounts of solids have accumulated within the bowl. Therefore, a centrifugal separator having a clean cycle that is activated at predetermined time intervals is generally ineffective in handling a process wherein the quantity of solids within the contaminated fluid varies.
Another disadvantage of many prior centrifugal separators relates to the speed at which the plow blade assembly is rotated relative to the bowl wall. Typically, in some prior art separators a brake is actuated to stop the plow blade assembly rotation so as to dislodge the particles accumulated on the bowl wall. The resulting interaction between the braked plow blade assembly and the rotating bowl causes the solids accumulated on the bowl wall to be dragged at a relatively high speed across the surface of the bowl wall. Often, the contaminated fluid contains abrasive particles that cause wear, erosion and other premature failure problems when dragged across the bowl surface.
Although the prior techniques of reducing bowl dynamic imbalance and overloading in centrifugal separators are steps in the right direction, the need for additional improvement still remains. The present invention satisfies this need in a novel and unobvious way.